Passage efficiency of radiotagged rainbow trout at the
Maple Hill fishway was 20 %. Based on our
professional opinion, coupled with radiotelemetric data
and underwater videography, it is highly likely that the
measured passage rate of 20 % was a conservative
underestimate of the efficiency of the Maple Hill fishway
for passing rainbow trout. It is likely that the true
passage rate (passage efficiency) was approximately 40 –
50 % (i.e., double the measured rate).

Upstream migration
of rainbow trout in the spring is triggered by increases
in river discharge as water temperatures increase above
6-7 ºC. River flows were exceptionally low in 2010 and
this may have negatively affected fish passage at the
Maple Hill dam. April 2010 discharge in the Saugeen River
was at summer low flow levels, and it is likely that
upstream passage at the Maple Hill fishway would be
greater under more typical spring flow conditions.

Rainbow trout
spent approximately four (4) days locating and using the
fishway. Much of this time was spent “upstream” from the
fishway in the dam tailrace. The Maple Hill fishway is
located near the turbine outflow where fish attraction is
greatest; however, some fish entered and remained in the
dam spillway for several days. Since the majority of the
Saugeen River flow at Maple Hill dam does not pass over
the dam structure, but rather is passed through the
turbines, it is likely that outflow from the turbines
facilitates conditions that attract fish to the fishway
entrance under current conditions. High discharge
events over the Maple Hill dam during the spring would
result in increased fish passage if a second fishway were
constructed near the dam with its entrance as close to the
dam face as possible.